In the fields of chemical and medical sciences, pharmacy and biotechnology, especially in the fields of environmental monitoring and food safety control, there is an increasing demand for the rapid analysis and real-time responses of specific substances such as certain contaminants in complex mixtures of related substances.
A conventional chemosensing approach or a conventional chemosensor which selectively recognizes and reversibly binds targeted molecular entities and yields measurable signals can be used for the purposes discussed above. The term of chemosensing refers to the recognition of targeted analytes via molecular-level sensors. In general, a chemosensor consists of (1) a molecular receptor, which can recognize and bind to its targeted analytes, and (2) a signal transducer that signals this binding event to the outside world. However, the specificity of conventional chemosensing approaches or chemosensors is usually limited to functional group level.
Molecularly imprinted polymer based (MIP-based) chemosensing approach or an MIP-based chemosensor selectively recognizes and reversibly binds targeted molecular entities and yields measurable signals, in a similar way as conventional chemosensing, except that the molecularly imprinted polymer based (MIP-based) chemosensor recognizes the molecular shape of its target analyte by molecular imprinting rather than chemical functionality recognition.
The term of molecularly imprinting refers to the induction of highly specific binding sites in synthetic polymers (referred to as the molecularly imprinted polymers—MIPs) by template-directed cross-linking of functional monomers. The process of molecular imprinting is schematically represented by FIG. 1.
As shown in FIG. 1, molecular imprinting approach involves formation of a template-functional monomer aggregate between a given template molecule and functional monomers (for example, functional monomers for non-covalent interactions, functional monomers for covalent interactions, and functional monomers for chelating interactions) in an appropriate solvent. The template-functional monomer aggregate is then fixed by cross-linking of functional monomers with cross-linkers. Subsequent removal of the template leaves binding sites within the polymer possessing both shape and the correct orientation of functional groups to allow specific re-binding of the template molecule and selective recognition of the imprint molecule.
In respect of the prior molecular imprinting strategies, which have been proposed for molecularly imprinted polymer based (MIP-based) chemosensing purpose, the interaction between functional monomers and the analytes is required in the molecular imprinting process as well as the subsequent analytes re-binding and chemosensing processes. The subsequent analyte's re-binding and chemosensing processes usually require the existence of some sort of intermolecular interaction between the target analytes and the signal transducer moiety. In other words, the subsequent analyte's re-binding and chemosensing process requires the existence of some sort of intermolecular interaction between the target analytes and the functional monomer. Therefore, the selection of appropriate signal transducer or functional monomer is important, which mainly depends on the type of intermolecular interaction between the target analytes and the signal transducer moiety, such as hydrogen bonding, dipole-dipole interactions and electron transfer.
However, analytes which lack the ability of intermolecular interaction with the signal transducer or functional monomer cannot be easily detected by this convenient molecularly imprinted polymer based (MIP-based) chemosensing approach because the analytes cannot intermolecularly interact with the signal transducer or functional monomer.